This invention relates to novel oxetanone derivative compounds and processes for producing such derivatives which are useful as lipase inhibitors. Further the invention relates to processes for producing salts and for producing pharmaceutical compositions compounds comprising at least one such oxetanone derivative or salt, as well as methods for using such compounds and compositions for inhibiting lipases. In one aspect the invention relates to lipase inhibitors which include on the same molecule an oxetanone derivative portion capable of inhibiting a lipase and a non-absorbable moiety such a polysaccharide, which are covalently linked or are in the form of a salt. In a preferred aspect of the invention the non-absorbable moiety is lipophilic and will associate with oils or fats. An absorbable oxetanone lipase inhibitor may be rendered non-absorbable by covalent linking it directly or indirectly to a non-absorbable moiety and thereby producing a novel non-absorbable lipase inhibitor.
Some lipase-inhibiting oxetanones and intermediates for making them are well known. See for example, U.S. Pat. Nos. 5,931,463, 5,175,186, 4.189,438 and 4,202,824. However, there is a need for improved processes for making oxetanones in commercial quantities that are have low toxicity and are essentially not absorbable by the digestive system of mammals such as dogs, cats, non-human primates and human primates.
Lipase inhibitors such as esterastin (2S, 3S, 5S) 3,5-hydroxy-2-hexadeca-7,10-dienoic 1,3-lactone), tetrahydroesterastin (2S, 3S, 5S) 3,5-di-hydroxy-2-hexylhexadecanoic 1,3-lactone, and the like (see U.S. Pat. No. 4,189,438), are well-known as lipase inhibitors and are useful as pancreatic cholesterol esterase inhibitors. While these lipase inhibitor can be obtained by cultivating microbes as described in U.S. Pat. No. 4,189,438, it is believed that examples of successful synthetic procedures for effectively making such compounds in commercially acceptable quantities from intermediates other than those obtained from microbes have not been described in the literature.
Further, esterastin and tetrahydroesterastin are excluded by proviso from the claims of the U.S. Pat. No. 5,175,186, which relates to a synthetic method for making certain analogs of esterastin and tetrahydroesteratin. The specification of that document does not illustrate the direct production of esterastin or tetrahydroesteratin or other (5S) analogs before the 2S, 3S oxetanone (lactone) ring structure is formed. Further page 6, lines 21-44, of the 5,175,186 patent points to an asymetrical hydrogenation synthesis step, which makes obtaining (2S, 3S, 5S) analog compounds before the direct closure of the oxetanone ring problematic. On page 6, when an intermediate compound having the 5 hydroxyl group in the R configuration (6R intermediate), is selectively hydrogenated only the (3S, 4S, 6R) intermediates result, which convert to a final compound having a 2S, 3S, 5R configuration. Likewise, when a only a 6S intermediate is used the (3R, 4R, 6S) hydrogenation intermediates result. The 5,175,186 patent does not illustrate a feasible and efficient solution for resolving such a synthetic difficulty prior to closure of the oxetanone ring.
Accordingly, there is a need in the art for an improved commercial process for efficiently making tetrahydroesterastin and its (2S, 3S, 5S) analogs in a enantiomeric excess of greater than 70% by the use of 2S, 3S, 5S intermediate compounds which are formed prior to the formation of the oxetanone ring structure.
In one aspect the present invention relates to novel process for making in at least 70% enantiomeric purity a (3S, 4S, 6S) oxetanone compound of the formula (I),: 
or a salt thereof
wherein:
R1 and R3 are each independently a C1 to C18 straight or branched alkyl hydrocarbon chain, and
R2 is hydrogen or an alcohol protecting group R10, wherein R10 can be replaced by a hydrogen atom via ester hydrolysis or hydrogenation ether degradation, comprising the steps of:
(a) selectively hydrogenating a composition comprising a compound which is a member selected from the group consisting of (6R) tetrahydro-2H-pyran-2-one compound of formula (II) and (6R) 5,6-dihydro-2H-pyran-2,4-dione of formula (IIa): 
wherein
R5 is hydrogen or an alcohol protecting group, which can be replaced by a hydrogen atom via hydrogenation, and R1 and R3 are defined as in formula (I), by hydrogenating the compound of formula II with a hydrogenation catalyst selected from the group consisting of PtO2, Raney Nichel and the like, and exchanging hydrogen atoms at the 3 and 4 ring positions or oxidizing the 4-oxo group to provide a (3S, 4S, 6R) 4-hydroxy-tetrahydro-2H-pyran-2-one compound of the formula (III): 
wherein R1 and R3 are defined as in formula (I);
(b) re-protecting the 4-hydroxy group of the compound of formula (II) produced in (a) with an ether protecting group R6, which can be replaced by a hydrogen atom via ester hydrolysis or hydrogenation ether degradation, opening the lactone ring and esterifying the resulting free acid group to provide a (2S, 3S, 5R) [R7] 2-[R3]-3-[R6xe2x88x92oxy]-5-[hydroxy, R1] pentanoic acid ester compound of the formula (IV): 
wherein
R1 and R3 are defined as in formula (I),
R6 is an alcohol protecting group, which can be replaced by a hydrogen atom via ester hydrolysis or hydrogenation ether degradation, and
R7 is an ester group which can be removed by base or acid hydrolysis, or by hydrogenation;
(c) inverting the chirality of the 5-hydroxy group of the compound of formula (IV) produced in step (b), wherein the inversion comprises a step which is a member selected from the group consisting of
(i) a Mitsunobu reaction.
(ii) esterifying the 5-hydroxy group to a carboxylic acid ester such as the trichloroacetic acid ester, and the like, and hydrolyzing the resultant ester in a water ether solvent such as 3:1 H2O/ dioxane, and
(iii) esterifying the 5-hydroxy group to a sulfonic acid ester, such as p-toluene sulfonic acid ester and the like, and reacting the ester with an excess of an organic acid salt selected from the group consising of potassium acetate, sodium acetate, tetraethylammonium acetate, and the like, to provide an ester exchange with the organic acid,
wherein the free inverted (5S) 5-hydroxy group of (i) and (ii) is esterified with a hydroxy protecting group R10 which can be which can be replaced by a hydrogen atom via ester hydrolysis or hydrogenation ether degradation, to provide a compound of the formula (V): 
wherein
R1 and R3 are defined as in formula (I),
R6 is an alcohol protecting group, which can be replaced by a hydrogen atom via ester hydrolysis or hydrogenation ether degradation,
R9 is an ester group which can be removed by base or acid hydrolysis, or by hydrogenation, and
R10 is an alcohol protecting group, which can be replaced by a hydrogen atom via ester hydrolysis or hydrogenation ether degradation, and wherein R10 is selectively removable with respect to the R6 alcohol protecting group; and
(d) selectively removing the R6 alcohol protecting group and R9 ester group of the compound of formula (V) produced in (c), and cyclizing the 3 position alcohol group with the 1 position acid group using a lactone cyclizing catalyst, such as benzene-sulphonyl chloride, in a solvent such as pyridine at a temperature of about xe2x88x9210 to 10xc2x0 C., and optionally replacing the R10 alcohol protecting group of formula (V) with a hydrogen atom, to yield a (3S, 4S, 6S) oxetanone compound of the formula (I): 
or a salt thereof.
In a preferred aspect, the process provides a compound of formula (I) wherein R1 is undecyl, R3 is hexyl and R2 is hydrogen, which is (2S, 3S, 5S) tetrahydroesterastin.
In another aspect the present invention relates to coupling such compound of formula (I) to an acyl compound via an acid or base esterification procedure without inversion of the 5S hydroxy group.
In another aspect the present invention provides a novel intermediate (2S, 3S, 5S) compound of the formula: 
wherein:
R1 and R3 are each independently a C1 to C18 straight or branched alkyl hydrocarbon chain, and
R2 is hydrogen or an alcohol protecting group R10, wherein R10 can be replaced by a hydrogen atom via ester hydrolysis or hydrogenation ether degradation, and R10 is selectively removable with respect to the R6 alcohol protecting group,
R6 is an alcohol protecting group, which can be replaced by a hydrogen atom via ester hydrolysis or hydrogenation ether degradation, and
R9 is an ester group which can be removed by base or acid hydrolysis, or by hydrogenation,
or, a salt thereof.
In a preferred aspect, the invention providessuch an intermediate compound wherein R1 is undecyl or heptadecyl and R3 is ethyl or hexyl, or a salt thereof.
In accordance with the present invention and as used herein, the following terms are defined with the following meanings, unless explicitly stated otherwise.
The term xe2x80x9calkenylxe2x80x9d refers to a trivalent straight chain or branched chain unsaturated aliphatic radical. The term xe2x80x9calkinylxe2x80x9d (or xe2x80x9calkynylxe2x80x9d) refers to a straight or branched chain aliphatic radical that includes at least two carbons joined by a triple bond. If no number of carbons is specified alkenyl and alkinyl each refer to radicals having from 2-12 carbon atoms.
The term xe2x80x9calkylxe2x80x9d refers to saturated aliphatic groups including straight-chain. branched-chain and cyclic groups having the number of carbon atoms specified, or if no number is specified, having up to 12 carbon atoms. The term xe2x80x9ccycloalkylxe2x80x9d as used herein refers to a mono-, bi-, or tricyclic aliphatic ring having 3 to 14 carbon atoms and preferably 3 to 7 carbon atoms.
As used herein, the terms xe2x80x9ccarbocyclic ring structure xe2x80x9cand xe2x80x9d C3-16 carbocyclic mono, bicyclic or tricyclic ring structurexe2x80x9d or the like are each intended to mean stable ring structures having only carbon atoms as ring atoms wherein the ring structure is a substituted or unsubstituted member selected from the group consisting of: a stable monocyclic ring which is aromatic ring (xe2x80x9carylxe2x80x9d) having six ring atoms; a stable monocyclic non-aromatic ring having from 3 to 7 ring atoms in the ring; a stable bicyclic ring structure having a total of from 7 to 12 ring atoms in the two rings wherein the bicyclic ring structure is selected from the group consisting of ring structures in which both of the rings are aromatic, ring structures in which one of the rings is aromatic and ring structures in which both of the rings are non-aromatic; and a stable tricyclic ring structure having a total of from 10 to 16 atoms in the three rings wherein the tricyclic ring structure is selected from the group consisting of: ring structures in which three of the rings are aromatic, ring structures in which two of the rings are aromatic and ring structures in which three of the rings are non-aromatic. In each case, the non-aromatic rings when present in the monocyclic, bicyclic or tricyclic ring structure may independently be saturated, partially saturated or fully saturated. Examples of such carbocyclic ring structures include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, adamantyl, cyclooctyl, [3.3.0]bicyclooctane, [4.3.0]bicyclononane, [4.4.0]bicyclodecane (decalin), 2.2.2]bicyclooctane, fluorenyl, phenyl, naphthyl, indanyl, adamantyl, or tetrahydronaphthyl (tetralin). Moreover, the ring structures described herein may be attached to one or more indicated pendant groups via any carbon atom which results in a stable structure. The term xe2x80x9csubstitutedxe2x80x9d as used in conjunction with carbocyclic ring structures means that hydrogen atoms attached to the ring carbon atoms of ring structures described herein may be substituted by one or more of the substituents indicated for that structure if such substitution(s) would result in a stable compound.
The term xe2x80x9carylxe2x80x9d which is included with the term xe2x80x9ccarbocyclic ring structurexe2x80x9d refers to an unsubstituted or substituted aromatic ring, substituted with one, two or three substituents selected from loweralkoxy, loweralkyl, loweralkylamino, hydroxy, halogen, cyano, hydroxyl, mercapto, nitro, thioalkoxy, carboxaldehyde, carboxyl, carboalkoxy and carboxamide, including but not limited to carbocyclic aryl, heterocyclic aryl, and biaryl groups and the like, all of which may be optionally substituted. Preferred aryl groups include phenyl, halophenyl, loweralkylphenyl, napthyl, biphenyl, phenanthrenyl and naphthacenyl.
The term xe2x80x9carylalkylxe2x80x9d which is included with the term xe2x80x9ccarbocyclic arylxe2x80x9d refers to one, two, or three aryl groups having the number of carbon atoms designated, appended to an alkyl group having the number of carbon atoms designated. Suitable arylalkyl groups include, but are not limited to, benzyl, picolyl, naphthylmethyl, phenethyl, benzyhydryl, trityl, and the like, all of which may be optionally substituted.
The terms xe2x80x9chaloxe2x80x9d or xe2x80x9chalogenxe2x80x9d as used herein refer to Cl, Br, F or I substituents. The term xe2x80x9chaloalkylxe2x80x9d, and the like, refer to an aliphatic carbon radicals having at least one hydrogen atom replaced by a Cl, Br, F or I atom, including mixtures of different halo atoms. Trihaloalkyl includes trifluoromethyl and the like as preferred radicals, for example.
The term xe2x80x9cmethylenexe2x80x9d refers to xe2x80x94CH2xe2x80x94.
In one embodiment the present invention relates to novel process for making in at least 70% enantiomeric purity a (3S, 4S, 6S) oxetanone compound of the formula (I),: 
or a salt thereof
wherein:
R1 and R3 are each independently a C1 to C18 straight or branched alkyl hydrocarbon chain, and
R2 is hydrogen or an alcohol protecting group R10, wherein R10 can be replaced by a hydrogen atom via ester hydrolysis or hydrogenation ether degradation. comprising the steps of:
(a) selectively hydrogenating a composition comprising a compound which is a member selected from the group consisting of (6R) tetrahydro-2H-pyran-2-one compound of formula (II) and (6R) 5,6-dihydro-2H-pyran-2,4-dione of formula (IIa): 
xe2x80x83wherein
R5 is hydrogen or an alcohol protecting group, which can be replaced by a hydrogen atom via hydrogenation, and R1 and R3 are defined as in formula (I), by hydrogenating the compound of formula II with a hydrogenation catalyst selected from the group consisting of PtO2, Raney Nichel and the like, and exchanging hydrogen atoms at the 3 and 4 ring positions or oxidizing the 4-oxo group to provide a (3S, 4S, 6R) 4-hydroxy-tetrahydro-2H-pyran-2-one compound of the formula (III): 
xe2x80x83wherein R1 and R3 are defined as in formula (I);
(b) re-protecting the 4-hydroxy group of the compound of formula (II) produced in (a) with an ether protecting group R6, which can be replaced by a hydrogen atom via ester hydrolysis or hydrogenation ether degradation, opening the lactone ring and esterifying the resulting free acid group to provide a (2S, 3S, 5R) [R7] 2-[R3]-3-[R6xe2x88x92-oxy]-5-[hydroxy, R1 pentanoic acid ester compound of the formula (IV): 
xe2x80x83wherein
R1 and R3 are defined as in formula (I),
R6 is an alcohol protecting group, which can be replaced by a hydrogen atom via ester hydrolysis or hydrogenation ether degradation, and
R7 is an ester group which can be removed by base or acid hydrolysis, or by hydrogenation;
(c) inverting the chirality of the 5-hydroxy group of the compound of formula (IV) produced in step (b), wherein the inversion comprises a step which is a member selected from the group consisting of
(i) a Mitsunobu reaction,
(ii) esterifying the 5-hydroxy group to a carboxylic acid ester such as the trichloroacetic acid ester, and the like, and hydrolyzing the resultant ester in a water ether solvent such as 3:1 H2O/dioxane, and
(iii) esterifying the 5-hydroxy group to a sulfonic acid ester, such as p-toluene sulfonic acid ester and the like, and reacting the ester with an excess of an organic acid salt selected from the group consising of potassium acetate, sodium acetate. tetraethylammonium acetate, and the like, to provide an ester exchange with the organic acid,
wherein the free inverted (5S) 5-hydroxy group of (i) and (ii) is esterified with a hydroxy protecting group R10 which can be which can be replaced by a hydrogen atom via ester hydrolysis or hydrogenation ether degradation, to provide a compound of the formula (V): 
wherein
R1 and R3 are defined as in formula (I),
R6 is an alcohol protecting group, which can be replaced by a hydrogen atom via ester hydrolysis or hydrogenation ether degradation,
R9 is an ester group which can be removed by base or acid hydrolysis, or by hydrogenation, and
R10 is an alcohol protecting group, which can be replaced by a hydrogen atom via ester hydrolysis or hydrogenation ether degradation, and wherein R10 is selectively removable with respect to the R6 alcohol protecting group; and
(d) selectively removing the R6 alcohol protecting group and R9 ester group of the compound of formula (V) produced in (c), and cyclizing the 3 position alcohol group with the 1 position acid group using a lactone cyclizing catalyst, such as benzene-sulphonyl chloride, in a solvent such as pyridine at a temperature of about xe2x88x9210 to 10xc2x0 C., and optionally replacing the R10 alcohol protecting group of formula (V) with a hydrogen atom, to yield a (3S, 4S, 6S) oxetanone compound of the formula (I): 
xe2x80x83or a salt thereof
In a preferred aspect, the process provides a compound of formula (I) wherein R1 is undecyl, R3 is hexyl and R2 is hydrogen, which is (2S, 3S, 5S) tetrahydroesterastin.
In another aspect the present invention relates to coupling such compound of formula (I) to an acyl compound via an acid or base esterification procedure without inversion of the 5S hydroxy group.
In another aspect the present invention provides a novel intermediate (2S, 3S, 5S) compound of the formula: 
wherein:
R1 and R3 are each independently a C1 to C18 straight or branched alkyl hydrocarbon chain, and
R2 is hydrogen or an alcohol protecting group R10, wherein R10 can be replaced by a hydrogen atom via ester hydrolysis or hydrogenation ether degradation, and R10 is selectively removable with respect to the R6 alcohol protecting group,
R6 is an alcohol protecting group, which can be replaced by a hydrogen atom via ester hydrolysis or hydrogenation ether degradation, and
R9 is an ester group which can be removed by base or acid hydrolysis, or by hydrogenation,
or, a salt thereof.
In a preferred aspect, the invention provide such intermediate compounds wherein R1 is undecyl or heptadecyl and R3 is ethyl or hexyl, or a salt thereof.
In a preferred aspect the above process comprises making a (3S, 4S, 6S) oxetanone compound of the formula (I), or a salt thereof, in at least 90% enantiomeric purity:
In another preferred aspect the present invention provides a process for making a compound wherein R1 is undecyl or heptadecyl and R3 is ethyl or hexyl in at least 90% enantiomeric purity:
In one aspect the invention provides a process wherein the compound of formula (II) in step (a) is present at a ratio of from 90 to 100% with respect to the corresponding (6S) enantiomer, and comprises the step of isolating such a compound of formula (II) in an enantiomeric excess of from 90 to 100% with respect to the corresponding (6S) enantiomer.
In a preferred aspect the invention provides a process wherein the compound of formula (II) in step (a) is present at a ratio of greater than 97% with respect to the corresponding (6S) enantiomer, and comprises the step of isolating such a compound of formula (II) in an enantiomeric excess of greater than 97% with respect to the corresponding (6S) enantiomer.
The present invention provides a process as described above, which further comprises isolating a compound which is a member selected from the group consisting of the 6R compound of formula (IV), or its corresponding (6R, 3RS, 4RS) racemate with an alcohol protected 3 hydroxyl group, from a compound which is a member selected from the 6S, 3R, 4R enantiomer with an alcohol protected 3 hydroxyl group corresponding to the compound in formula (IV) and a compound which is the (6S, 3RS, 4RS) racemate corresponding to the compound of formula (IV), comprising a separation step with is a member selected from the group consisting of:
(i) selectively esterifying the 6-position hydroxyl group in the presence of a lipase such as PS 30, porcine pancreas lipase, and the like, and separating the ester from the alcohol,
(ii) selectively hydrolyzing an ester an ester of the 6-position hydroxyl group via a lipase such as PS 30, porcine pancreas lipase, and the like, and separating the ester from the alcohol,
(iii) forming a chiral salt with a chiral alcohol resolving agent such as L-alaninol, D-alaninol, L-tartaric acid, D-tartaric acid, S-methylbenzyl-amine, D-methylbenzylamine in an appropriate solvent such as methyl acetate, and the like, and separating the two enantiomers by re-crystallization; and
(iv) other known chiral alcohol separating procedures,
and removing any ester or protecting groups from the 6R chiral hydroxyl group.
In another preferred aspect, the present invention provides such a process which further comprises the steps of
(a) inverting the 5S hydroxyl group of a (2R, 3R, 5S or 2RS, 3RS, 5S) [R7] 2-[R3]-3-[R6xe2x88x92oxy]-5-[hydroxy, R1] pentanoic acid ester compound of the formula (VII): 
xe2x80x83wherein
R1, R3, R6 and R7 are defined as in formula IV; wherein the inversion comprises a step which is a member selected from the group consisting of
(i) a Mitsunobu reaction, and freeing the hydroxyl group
(ii) esterifying the 5-hydroxy group to a carboxylic acid ester such as the trichloroacetic acid ester, and the like, and hydrolyzing the resultant ester in a water ether solvent such as 3:1 H2O/dioxane to the inverted hydroxyl group,
(iii) esterifying the 5-hydroxy group to a sulfonic acid ester, such as p-toluene sulfonic acid ester and the like, and reacting the ester with an excess of an organic acid salt selected from the group consising of potassium acetate, sodium acetate, tetraethylammonium acetate, and the like, to provide an ester exchange with the organic acid, and hydrolyzing the organic acid ester to the inverted hydroxyl group,
(iv) other known chiral alcohol inversion procedures,
(b) hydrolyzing the R7 ester group to provide the free acid compound of the formula (VIII): 
xe2x80x83wherein
R1, R3 and R6 and R7 are defined as in formula (VII), and
(c) cyclizing the inverted alcohol group of the compound of formula (VIII) with the 1 position acid group in the presence of a lactone cyclizing catalyst such as tonuene-4-sulfonic acid monohydrate in an alcohol at about 50-60xc2x0 C. to provide a 6R tetrahydro-2H-pyran-2-one compound of formula (IX): 
xe2x80x83wherein
R1, R3, R6 and R7 are defined as in formula (VIII);
and
(d) selectively hydrogenating the (6R) tetrahydro-2H-pyran-2-one compound of formula (IX) with a hydrogenation catalyst selected from the group consisting Of PtO2, Raney Nichel and the like, and exchanging hydrogen atoms at the 3 and 4 ring positions to provide a (3S, 4S, 6R) 4-hydroxy-tetrahydro-2H-pyran-2-one compound of the formula (IV): 
xe2x80x83wherein R1 and R3 are defined as in formula (I).
The intermediate compounds of formulae (II) and (IV) can be efficiently made from commercially feasible materials by adapting several methods known in the art and by refining the synthesis to avoid unnecessary or costly steps. Further, the following non-limiting reaction schemes, some steps of which are novel, are merely to exemplify the invention.
A process for making an intermediate compound for synthesizing a compound of the formula: 
comprising the steps of:
treating dodecyl aldehyde (lauraldehyde) with a saturated aqueous solution of a bisufite such as sodium bisulfite to form a bisulfite salt of the formula: 
xe2x80x83(b) reacting the bisulfite salt with a 2-haloacetic acid R ester, such as 2 bromoacetic acid ethyl ester in a suitable solvent such as THF and water and in the presence of a catalytic amount of an acid such as HCl to produce a ketone derivative of the formula: 
xe2x80x83(c) reducing the ketone derivative with NaBH4, or the like, and optionally resolving the R and S enantiomer by forming an ester under chiral resolving conditions, such as esterifying the alcohol in the presence of the pseudomonas lipase PS 30 and the like, or by reducing the ketone carbonyl group with a chiral hydrogenation catalyst, at a temperature from 0xc2x0 C. to 50xc2x0 C., preferably at room temperature, in a suitable solvent, such as ethanol and the like, or reducing the ketone group with a chiral borane such as DIP-Cl (Aldrich) and protecting the alcohol with a protecting group (P1), such as t-butylidimethylsilyl by reaction with t-butyldimethylchlorosilane in dimethylformamide (DMF), to provide a compound of the formula: 
xe2x80x83(d) reacting the protected alcohol with at least one equivalent of a base such as NaOH followed by at least 1 equivalent of HCl to provide the free acid compound, and reacting the mono free acid with an acid reducing agent such as BF3xe2x80x94THF to produce the corresponding aldehyde of the formula: 
xe2x80x83(e) reacting the aldehyde with a 2-halogenoctanoate (such as ethyl 2-bromooctanoate) to produce a ketone compound of the formula: 
xe2x80x83(f) reducing the 3 ketone derivative with NaBH4, or the like, then removing the P1 protecting group from the 5 hydroxy in a solvent such as an alcohol, e.g., ethanol in the presence of an acid catalyst such as pyridinium-4-toluenesulphoneate or tetrabutylammonium fluoride trihydrate in THF while heating at about 50-65xc2x0 C., followed by hydrogenating the ester group with hydrogen and Pd/C to yield the free acid diol as follows: 
xe2x80x83(g) and then cyclizing the 5R alcohol with the free acid to provide a 6R pyranolone ring by heating the free acid compound at a temperature from 50xc2x0 C. to 60xc2x0 C. in ethanol in the presence of toluene-4-sulfonic acid to provide a compound of the formula: 
xe2x80x83which may be utilized as the formula (II) compound described above.
Alternatively, the chiral ketone reducing agent utilized to reduce the beta oxo dodecanoic acid can be omitted to obtain a racemate. The racemate can be utilized as the formula (II) compound, followed by resolving the resulting (2S, 3S, 5R) formula (IV) enantiomer from its (2R, 3R, 5S) formula (VII) enantiomer.
Another process for making an intermediate compound for synthesizing a compound of the formula: 
comprises the steps of:
xe2x80x83(a) treating dodecyl halide (lauric acid chloride) with a N,O-dimethylhydroxyl- amine hydrochloride in a 1:1.5 ratio in acetonitrile, triethylamine and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and stirring at room temperature for about 5 hours to provide a compound of the formula: 
xe2x80x83(b) reacting the N-methoxymethyl amide carboxylic acid derivative with an organometallic salt of an acetic acid R ester (or a salt of a two halo acetic acid R ester), such as 2-lithium acetic acid ethyl ester in a suitable solvent such as dry THF under nitrogen or argon and the reaction is quenched with an acid such as HCl to produce a ketone derivative of the formula: 
xe2x80x83(c) forming the tetradecyl acyl halide (for example the acid chloride) of the ketone compound and reacting it with a N,O-dimethylhydroxyl- amine hydrochloride in a 1:1.5 ratio in acetonitrile, triethylamine and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and stirring at room temperature for about 5 hours to provide a compound of the formula: 
xe2x80x83(d) reacting the N-methoxymethyl amide carboxylic acid derivative with an alpha organometallic salt of an lower alkyl acid R ester (or a salt of an alpha halo lower alkyl acid R ester), such as 2-lithium octanoic acid ethyl ester in a suitable solvent such as dry THF under nitrogen or argon and quenching the reaction with an acid such as HCl, and the like to produce a 3,5 diketone derivative of the formula: 
xe2x80x83(e) reducing the 3,5 diketone acid derivative with NaBH4, or the like, to yield the free acid diol as follows: 
and
xe2x80x83(f) cyclizing the 5RS alcohol with the free acid to provide a 6R pyranolone ring by heating the free acid compound at a temperature from 50xc2x0 C. to 60xc2x0 C. in ethanol in the presence of toluene-4-sulfonic acid to provide a compound of the formula: 
xe2x80x83which may be utilized as the formula (II) compound described above.
Alternatively, the diketone reduction step of step (e) can be conducted with a chiral borane reducing to obtain a (2RS, 3R, 5R) which when cyclized provides the (3RS, 4R, 6R) compound, which can be utilized as the formula (II) compound.
A further process for making an intermediate compound for synthesizing a compound 
comprises the steps of:
(a) reaction methyl 2-acetyloctanate (Aldrich 10887) with a organometallic base, such as butyllithium salt to deprotonate the tertiary carbon atom of the 2-acetyl group,
(b) reacting the lithium organometallic salt in a suitable solvent such as THF with a lauric acid halide (dodecoyl chloride) of the formula: 
xe2x80x83to provide a 3,5 diketone compound of the formula: 
xe2x80x83(c) reducing the 3,5 diketone acid derivative with NaBH4, or the like, to yield the free acid diol as follows: 
and
(d) cyclizing the 5RS alcohol with the free acid to provide a 6R pyranolone ring by heating the free acid compound at a temperature from 50xc2x0 C. to 60xc2x0 C. in ethanol in the presence of toluene-4-sulfonic acid to provide a compound of the formula: 
xe2x80x83which may be utilized as the formula (II) compound described above.
Alternatively, the diketone reduction step of step (c) can be conducted with a chiral borane reducing agent to obtain a (2RS, 3R, 5R) which when cyclized provides the (3RS, 4R, 6R) compound, which can be utilized as the formula (II) compound.
In one aspect of the present invention, there is provided a chiral alcohol resolution process step which incorporates a lipase to hydrolyze esters of the intermediate alcohols, or to be present during an esterification step, wherein the lipase may be a lipase such as the pseudomonas PS 30, pig pancreas lipase, and the like.
The (2S, 3S, 5S) oxetanone compounds provided by the processes according to the invention may be linked to other compounds or a support by esterifying with an acyl, acyl halide, or by a transesterification process. In a preferred embodiment the lipase inhibitiors according to the invention are linked via a terminal ether/terminal ester bridge, to a oil or lipid absorbable polymer moiety. Preferably, the free 5-hydroxyl (2S, 3S, 5S) compounds are linked under acidic conditions to a polysaccharide such as chitosan, which polysaccharide has been modified to have an acyl, or acyl halide attachment group.
Non-limiting examples of preferred bridges between the lipase inhibitor oxetanone moiety produced according to the present invention and the polymer moiety includes at least one ether bridge formed from an alcohol group on the polymer moiety and at least one ester or carboxamide bond between the 5-hydroxy group of the oxetanone. Further preferred is a process for producing a compound wherein at least one amino acid derivative is located in the bridge, and is bound directly or indirectly to the 5 hydroxyl position on the 1,3 oxetanone moiety via an ester linkage.
The preferred compounds produced from such linkage with a polysaccharide also includes their pharmaceutically acceptable isomers, hydrates, solvates, salts and prodrug derivatives.
A preferred aspect of the present invention relates to a process for making novel oxetanone derivatives of the formula Ia, as follows: 
wherein:
t is an integer from 0 to 1
Xxe2x80x94Oxe2x80x94Q is an ether linkage wherein:
X of the ether linkage is a bridging group, and
Q of the ether linkage is a polysaccharide of a sufficient molecular weight or property that such polysaccharide is not absorbed by the digestive system of a mammal such as a dog, cat, non-human primate or a human primate, which polysaccharide is further defined below;
R1 and R3 is defined as in formula (I) of the (2S, 3S, 5S) 5-hydroxyl oxetanone compounds, produced by a process according to the invention as described above,;
R1a is a member selected from the group consisting of:
Hydrogen,
Ar,
Arxe2x80x94C1-5-alkyl and
C1-10-alkyl interrupted by 0-3 members independently selected from the group consisting of an oxygen atom, a sulfur atom, a sulfinyl group, a sulfonyl group, a xe2x80x94N(xe2x80x94R4a group, a xe2x80x94C(xe2x95x90O)xe2x80x94N(xe2x80x94R4a group, and a xe2x80x94N(xe2x80x94R4a)xe2x80x94C(xe2x95x90O)xe2x80x94 group, wherein 0-3 carbon atoms of the C1-10-alkyl group can be substituted independently by a member selected from the group consisting of a hydroxy group, thiol group, C1-10-alkoxy group, a C1-10-alkylthio group, a xe2x80x94N(xe2x80x94R5a,xe2x80x94R6a) group, a xe2x80x94C(xe2x95x90O)xe2x80x94N(R7a, xe2x80x94R8a) group, and a xe2x80x94N(xe2x80x94R9a)xe2x80x94C(xe2x95x90O)xe2x80x94R10a group;
R2a is a member selected from the group consisting of:
hydrogen and C1-6-alkyl, or R2a taken with R1a forms a 4-6 membered saturated ring containing 0-4 nitrogen atoms wherein the ring may be substituted by 0-4 R11 groups:
R4a-R10a are each independently a member selected from the group consisting of:
hydrogen and C1-6-alkyl;
n is an integer of 0-3;
and all pharmaceutically acceptable isomers, salts, hydrates, solvates and prodrug derivatives thereof.
A preferred compound according to formula Ia is a compound wherein X is a member selected from the group consisting of:
xe2x80x94(C(xe2x95x90O))0-1xe2x80x94Xaxe2x80x94,
wherein Xa is a member selected from the group consisting of:
a straight or branched chained divalent C1-17-alkylene group which is saturated or optionally interrupted by up to eight double or triple bonds;
a straight or branched chained divalent C1-17-alkylene group which is saturated or optionally interrupted by one or more members selected from the group consisting of:
an oxygen atom,
a sulfur atom,
a sulfonyl group,
a sulfinyl group,
a substituted or unsubstituted 6-10 member monocyclic or bicyclic aryl or heteroaryl group having from 1-4 ring hetero atoms selected from the group consisting of O, N, S,
a xe2x80x94NHxe2x80x94 group, wherein the hydrogen atom may be replaced with a C1-10 alkyl group
a xe2x80x94C(xe2x95x90O)xe2x80x94 group,
a xe2x80x94NHxe2x80x94C(xe2x95x90O)xe2x80x94 group, wherein the hydrogen atom may be replaced with a C1-10 alkyl group and
a xe2x80x94C(xe2x95x90O)xe2x80x94NHxe2x80x94 group, wherein the hydrogen atom may be replaced with a C1-10 alkyl group
a straight or branched chained divalent C1-17-alkylene group which is saturated or optionally interrupted by up to eight double or triple bonds and is interrupted in a position other than alpha to an unsaturated carbon atom by one or more members selected from the group consisting optionally interrupted by one or more members selected from the group consisting of:
an oxygen atom,
a sulfur atom,
a sulfonyl group,
a sulfinyl group,
a substituted or unsubstituted 6-10 member monocyclic or bicyclic aryl or heteroaryl group having from 1-4 ring hetero atoms selected from the group consisting of O, N, S,
a xe2x80x94NHxe2x80x94 group, wherein the hydrogen atom may be replaced with a C1-10 alkyl group
a xe2x80x94C(xe2x95x90O)xe2x80x94 group,
a xe2x80x94NHxe2x80x94C(xe2x95x90O)xe2x80x94 group, wherein the hydrogen atom may be replaced with a C1-10 alkyl group and
a xe2x80x94C(xe2x95x90O)xe2x80x94NHxe2x80x94 group, wherein the hydrogen atom may be replaced with a C1-10 alkyl group
divalent phenylene or divalent naphthylene substituted on the ring structure by 0-4 members selected from the group consisting of xe2x80x94C1-6-alkyloxy-C1-6-alkyl, xe2x80x94C1-6-alkylthio-C1-6-alkyl, xe2x80x94C1-6-alkyl-OH and -C1-6-alkyl-SH;
divalent biphenylene substituted by 0-6 members selected from the group consisting of xe2x80x94C1-6-alkyloxy-C1-6-alkyl, xe2x80x94C1-6-alkylthio-C1-6-alkyl, xe2x80x94C1-6-alkyl-OH and xe2x80x94C-1-6-alkyl-SH;
phenoxyphenylene substituted by 0-6 members selected from the group consisting of xe2x80x94C1-6-alkyloxy-C1-6-alkyl, xe2x80x94C-1-6-alkylthio-C1-6-alkyl, xe2x80x94C1-6-alkyl-OH and xe2x80x94C1-6-alkyl-SH;
divalent phenylthiophenylene substituted by 0-6 members selected from the group consisting of xe2x80x94C1-6-alkyloxy-C1-6-alkyl, xe2x80x94C1-6-alkylthio-C1-6-alkyl, xe2x80x94C1-6-alkyl-OH and xe2x80x94C1-6-alkyl-SH; and
and all pharmaceutically acceptable isomers, salts, hydrates, solvates and prodrug derivatives thereof.
More preferred is compound according to formula Ia, wherein X is a member selected from the group consisting of:
xe2x80x94(C(xe2x95x90O))xe2x80x94Xaxe2x80x94,
and Xa is a member selected from the group consisting of:
a straight or branched chained divalent C1-17-alkylene group which is saturated or optionally interrupted by up to eight double or triple bonds.
Further preferred are compounds according to formula Ia, wherein R1 is undecyl, R3 is hexyl, R1a is straight or branched chain C1-C8 alkyl, R2a is hydrogen and X is a member selected from the group consisting of:
xe2x80x94(C(xe2x95x90O))xe2x80x94Xaxe2x80x94,
and Xa is a member selected from the group consisting of divalent saturated C5-C18 alkylene, and more preferably, Xa is a divalent saturated pentylene or undecylene group, or a salt thereof.
The lipase inhibitor compounds, polymer moieties and bridging groups of the present invention may be synthesized or readily obtained from commercially available sources. Preferably, the (2S, 3S, 5S) 5-hydroxyl oxetanone lipase inhibitor compounds are obtained by a process as described above. Polymer bridging groups, bridge coupling processes and compound purification methods are described and referenced in standard textbooks, particularly the coupling of alcohol groups via diether bridges, ether/ester bridges, ether/ketone bridges and the like. Standard polymer textbooks reference typical bifunctional bridging groups and coupling procedures.
Starting materials used in any of these methods are commercially available from chemical vendors such as Aldrich, Sigma, Nova Biochemicals, Bachem Biosciences, and the like, or may be readily synthesized by known procedures.
Reactions are carried out in standard laboratory glassware and reaction vessels under reaction conditions of standard temperature and pressure, except where otherwise indicated.
During the synthesis of these compounds, the functional groups may be protected by blocking groups to prevent cross reaction during the coupling procedure. Examples of suitable blocking groups and their use are described in xe2x80x9cThe Peptides: Analysis, Synthesis, Biologyxe2x80x9d, Academic Press, Vol. 3 (Gross, et al., Eds., 1981) and Vol. 9 (1987), the disclosures of which are incorporated herein by reference. Alcohol and ester protecting group may also be utilized.
Lipase inhibitor moieties having a free hydroxy group such as the oxetanones described above, and the like, are easily coupled to a polymer moiety having free hydroxy groups such as cellulose, chitosan and other polysaccharides having free hydroxyl groups. One or both of the lipase inhibitor moiety and the polymer moiety may be derivitized to form part of the linking bridge prior to reacting with the other moiety. For example, a desired number of the hydroxy groups of the polysaccharides, such as chitosan, may be functionalized with a compound having a terminal acyl or ester group such as 6-bromohexanoic acid, 12-bromododecanoic acid, and the like, or an ester derivative of such acids, and subsequently the 5-hydroxyl group of the oxetanone lipase inhibitor molecule may be condensed with the ester group or a terminal acyl group (the acyl group may be modified with an halide group to an acyl halide group, such as the acyl chloride) to form an ester linkage with the ether bridged polymer moiety as shown in polysaccharide chemistry. In one procedure a polymer moiety such as chitosan can be reacted with a compound such as a halomethylbenzoic acid ester, loweralkyl 6-bromohexanoic acid, lower alkyl 12-bromododecanoic acid, or the like, and de-esterified to present a free acid group which may be, activated further by forming the acyl halider, and reacted with a terminal portion of the lipase inhibitor (which may have been esterified with a bridging compound which has a functional group capable of reacting with an ester or acyl group) to form an ester, ketone, or carboxamide with the optionally derivitized lipase inhibitor moiety.
In one preferred aspect of the invention, one of the two moieties is reacted with an asymmetrical halide/acyl bridging group, such as a terminal halide alkanoic acid of 1:1 to etherize a free hydroxyl group, replace a hydrogen atom on an amino group, or foom a ketone with an acid group, and the resulting intermediate can then be reacted with the an alcohol or amino moiety to form an ester group or a carboxamide group with a free alcohol group, or by replacing a nitrogen atom on a amino group. Particularly preferred polymer moieties are polysaccharides having multiple free hydroxyl group which after coupling may optionally be sulfonated to render the lipase moiety itself a lipase inhibitor compound. Etherification, amination and ketone formation procedures are well-known in the art and well within the routine skill of the ordinary practitioner. Further, other bridging groups and the techniques for binding a compound having a reactive functional group to a polymer moiety are well-known in the art. The preferred compounds also include their pharmaceutically acceptable isomers, hydrates, solvates, salts and prodrug derivatives.
The bridging group refers to a bifunctional chain or spacer group capable of reacting with one or more functional groups on a lipase inhibitor compound and then react with a second same or different functional group on a polymer compound in order to form a linked structure or conjugate between the two compounds. The bond formed between the bridging group and each of the two compounds is preferably of a type that is resistant to cleavage by the digestive environment, other than to inhibit a lipase by binding substantially irreversibly.
By appropriate selection of the type of bridging group reactant, different structural groups with various chemical properties can be incorporated into the resulting bridge and various types of lipase inhibitors can be connected to a nonabsorbable polymer moiety, such as a polysaccharide, and preferably to chitosan. Reaction temperatures and other reactions conditions, as well are reactant proportions are well within the skill of the ordinary polymer chemist practitioner. Other groups and modifications will be apparent to one of ordinary skill in the art from the above discussion.
The lipase inhibitor functionality of the coupled lipase inhibitors may be determined by well-known lipase inhibitor assays. A therapeutically effective amount of the bound lipase inhibitor may be administered to a patient. Additional fat binding polymers may optionally be added to the composition.
The following non-limiting reaction Schemes I, II, III and IV illustrate preferred embodiments of the invention with respect to making compounds according to the invention. 
Such chitosan derivatives provide a lipase inhibitor with very low absorption rates, and at such rates tetrahydroesterastin is not known to be substantially toxic.
Dosage formulations of the compounds of this invention to be used for therapeutic administration must be sterile. Sterility is readily accomplished by filtration through sterile membranes such as 0.2 micron membranes, or by other conventional methods. Formulations typically will be stored in lyophilized form or as an aqueous solution. The pH of the preparations of this invention typically will be between 3 and 11, more preferably from 5 to 9 and most preferably from 7 to 8. It will be understood that use of certain of the foregoing excipients, carriers, or stabilizers will result in the formation of cyclic polypeptide salts. While the preferred route of administration is by oral tablets, capsules or other unit dose mechanisms, such as liquids, other methods of administration are also anticipated such as in food stuffs, employing a variety of dosage forms. The compounds of this invention are desirably incorporated into food articles which may include fats to prevent their absorption.
The compounds of this invention may also be coupled with suitable polymers to enhance their therapeutic effects. Such polymers can include lipophilic polymers, such as polysaccharides and the like.
Therapeutically effective dosages may be determined by either in vitro or in vivo methods. For each particular compound of the present invention, individual determinations may be made to determine the optimal dosage required. The range of therapeutically effective dosages will naturally be influenced by the route of administration, the therapeutic objectives and the condition of the patient. For routes of administration, the lipase inhibitor activity, in view of the amount of fat consumed, must be individually determined for each inhibitor by methods well known in pharmacology. Accordingly, it may be necessary for the therapist to titer the dosage and modify the route of administration as required to obtain the optimal therapeutic effect. The determination of effective dosage levels, that is, the dosage levels necessary to achieve the desired result, will be within the ambit of one skilled in the art. Typically, applications of compound are commenced at lower dosage levels, with dosage levels being increased until the desired effect is achieved.
Typically, about 500 mg to 3 g of a lipase inhibitor compound or mixture of lipase inhibitor compounds of this invention, as the free acid or base form or as a pharmaceutically acceptable salt, is compounded with a physiologically acceptable vehicle, carrier, excipient, binder, preservative, stabilizer, dye, flavor etc., as called for by accepted pharmaceutical practice. The amount of active ingredient in these compositions is such that a suitable dosage in the range indicated is obtained. The addition, one or more other therapeutic ingredients such as a fat absorbing polysaccharide or fiber, a fat-specific lipase inhibitor or lipase, as well as other dietary agents may be utilized in therapeutically effective amounts.
Typical adjuvants which may be incorporated into tablets, capsules and the like are a binder such as acacia, corn starch or gelatin, and excipient such as microcrystalline cellulose, a disintegrating agent like corn starch or alginic acid, a lubricant such as magnesium stearate, a sweetening agent such as sucrose or lactose, or a flavoring agent. When a dosage form is a capsule, in addition to the above materials it may also contain a liquid carrier such as water, saline, a fatty oil. Other materials of various types may be used as coatings or as modifiers of the physical form of the dosage unit. Sterile compositions for injection can be formulated according to conventional pharmaceutical practice. Buffers, preservatives, antioxidants and the like can be incorporated according to accepted pharmaceutical practice.
In practicing the methods of this invention, the compounds of this invention may be used alone or in combination, or in combination with other therapeutic or diagnostic agents. In certain preferred embodiments, the compounds of this inventions may be coadministered along with other compounds typically prescribed for these conditions according to generally accepted medical practice, such as other weight control or lipase inhibitory products, cholesterol controlling drugs, and the like.
The compounds of this invention can be utilized in vivo, ordinarily in mammals such as non-human primates, humans, sheep, horses, cattle, pigs, dogs, cats, rats and mice, or in vitro.